Blind fastener construction

ABSTRACT

A blind fastener incorporates a carrier having a forming area or portion thereupon. Mounted on the carrier is a securement member having a deformable lower extremity. Also mounted on the carrier is a driver which is utilized to drive the securement member against the forming portion of the carrier to urge the extremity of the securement member into securement relationship with an object or objects with which the fastener is associated. The carrier incorporates an elongated shank having a frangible shear zone and the driver incorporates driving and locking portions also separated by a shear zone. The locking portion of the driver is received in a locking recess in the securement member and the shear zones are ruptured successively when predetermined loads are imposed thereupon resulting from the complete deformation of the extremity of the securement member and the reception of the locking portion in said locking recess.

United States Patent 119 Campbell et al. Mar. 12, 1974 BLIND FASTENERCONSTRUCTION [57] ABSTRACT [75] Inventors: James R. Campbell, SouthLaguna; A blind fastener incorporates a carrier having a form- MilesRainwater, Costa Mesa, both ing area or portion thereupon. Mounted onthe carrier of Calif. is a securement member having a deformable lower I1 extremity. Also mounted on the carrier is a driver [73] Asslgnee' g rgg gg g z git Momca which is utilized to drive the securement member a1y a against the forming portion of the carrier to urge the [22] Filed:Nov. 17, 1971 extremity of the securement member into securement [211 ppNOJ 199,514 relationship with an ob ect or ob ects w1th whrch theastener 1s assoclated.

The carrier incorporates an elongated shank having a [52] US. Cl. 85/77frangible Shear Zone and the driver incorporates [51] [111. CI. F161)13/06 driving and locking portions also Separated by a shear [581 ofSearch 85/77 zone. The locking portion of the driver is received in a85/ 75 29/512 522 locking recess in the securement member and the shearzones are ruptured successively when [56] Referencesclted predeterminedloads are imposed thereupon resulting UNITED STATES PATENTS from thecomplete deformation of the extremity of the 2,282,711 5/1942 Eklund85/72 Seeurement member and the reception of the locking 3,107,57210/1963 Orloff 85/73 X portion in said locking recess.

3,515,419 6/1970 Baugh 85/78 X Y 2,974,558 3/1961 Hodell 85/77 4 l 20Drawmg Flgul'es Primary Examiner-Ramon S. Britts Attomey, Agent, orFirm- -Mahoney, Schick & Ci slo mgmmnmzlm 3.796.125

sum 10F 3 Fig. i.

Fi 3. 4 Fi 2. T 5 7 JAMES R. CAMPBELL BY M/LEs RA/NWATER MAHONEY,HORNBAKER AND SCH/CK ATTORNEYS INVENTORS.

msminnm m4 3396.125

SHEET 2 0F 3 Fig. 9.

Fig. 32 2 2 4 Fig. I32 26 I22 56 L IO 9a |04 52 56 IB V 18 JAMES R.CAMPBELL MILES RAIN WATER MAHONE Y, HORNBAKER AND SCH/CK ATTORNEYS 45 lN VE N TORS PATENTEBIAR 12 1914 IN VENTORS.

JAMES R. CAMPBELL MILES RA/NWATER BYMA HONEY, HORNBA KER AND SCH/CKATTORNEYS BLIND FASTENER CONSTRUCTION BACKGROUND OF THE INVENTION Blindfasteners are commonly utilized in applications where the innerextremity of the fastener is inaccessible and, therefore, can not have acorresponding nut or other member applied thereto to cause the permanentsecurement of the same. For instance, blind fasteners of the rivetvariety are frequently used in aircraft fuselage and wing assembly wherethe location of a bucking bar in the interior of the structure to upsetthe inner extremity of a conventional rivet is not feasible. In suchapplications the blind rivet is inserted through an opening orcorresponding openings in the fuselage structure and the inner extremitythereof is upset by a wide variety of techniques, which include theutilization of a mandrel to collapse the inner end of a tubular rivetstructure, and the like. As a matter of fact, the larger number of blindfastener applications is to be found in the rivet art and there has beena significant advance in this art concomitant the increasedsophistication in aircraft and missile structures.

However, most blind fasteners, including those of the rivet variety, arecharacterized by the fact that the devices or techniques utilized indeforming or expanding the inner extremity of the rivet or blindfastener to form a securement head thereupon usually result inirregularly formed or deformed protuberances or bulbs on the inner endof the blind fastener construction. These protuberances or bulbs arefound upon and engage the sharp edge of the blind hole. Therefore, onlylineal engagement of the bulb with the blind sheet is achieved.Furthermore, the presence of burrs or sharp edges on the area of linealcontact will create incipient cracking in the bulb as it is formed thusmaterially reducing the effectiveness of the fastener grip.

In addition, since many of the blind fasteners now in use are of tubularconstruction, the relatively thin walls of the inner extremitiesthereof, when subjected to an expansive force, such as a collapsingmandrel, tend to immediately be subjected to incipient cracking whichis, in part, attributable to work hardening of the wall of the tubularstructure which is being deformed.

Therefore, the unpredictable results of prior art structures utilized toachieve the deformation of the inner extremities of blind fasteners hasprevented the application of such blind fasteners to structures whereloads are encountered which could be effectively sustained byconventional rivets or by conventional bolt type fasteners.Consequently, access doors and openings have had to be provided in thesecritical structural areas so that access may be had by the fabricatingmechanic to the interior surfaces of the structure to accomplish theupsetting of the interior extremities of rivets or the application ofnuts or other expedients to the inner extremities of bolt-typefasteners.

Most blind fasteners, which swell or bulge a tubular member, engage theblind side hole corner during the drive and create localized stresses onthe corner area and incipient fracture problems when this comer issignificantly burred.

Also the drawing together of the sheets being fastened involves arubbing action on this corner. Further, no commercially available blindfastener under all conditions of installation engage the blind sidesheet at an annular zone remote from the corner of the blind hole.

Another major disadvantage of conventional blind fasteners is that thereis usually no visual external indication of the condition of thefastener assembly after it has been operated upon to cause the upsettingof the inner extremity thereof to secure the structural elements towhich it is applied together. In other words, there is usually anexternal head structure of conventional configuration provided on theblind fastener and the only indication that something has taken place inthe internal structure of the aircraft, missile or other device to whichthe fastener is applied is that a mandrel or other member has beenpulled through the fastener construction to a predetermined extent.

OBJECTS AND SUMMARY OF THE INVENTION It is, therefore, a primary objectof our invention to provide a blind fastener which is particularlycharacterized by the fact that the blind securement head or ring formedthereupon engages the blind sheet or surface over a substantial annulararea removed from the sharp edge of the blind hole. Therefore,relatively massive area rather than linear contact is achieved.

Moreover, the incipient cracking and cutting of the securement bulbcharacteristic of prior art constructions is completely eliminated.

An associated object of the invention is the provision of a blindfastener of the aforementioned character wherein the fastener whendriven into the associated structures includes a locking ring at theexterior side of the structure and a securement ring on the blind sideof the structure with the full engagement of the locking ring indicatingcompleted fabrication of the securement ring.

Another object of our invention is the provision of a composite blindfastener which includes a carrier having a forming ring or portionthereupon or associated therewith which is intended to accomplish thefunction of deforming the associated extremity of a securement memberwhich is disposed in encompassing relationship with said carrier into asecurement ring, and which is adapted to be driven into operativeengagement with said forming area or portion by a contiguous driveraxially movable upon said carrier until the desired deformation of theaforesaid extremity of said securement member into the desiredsecurement ring has been accomplished.

An additional object of our invention is the provision of a blindfastener of the aforementioned character wherein the aforesaid carrierincorporates an elongated shank adjacent said forming area or ring andsaid'forming area or ring is separable from said shank by a frangibleshear or frangible area incorporated therein and susceptible to shearingor breaking off when the aforesaid complete deformation of the lowerextremity of a securement member of the fastener into a securement ringis accomplished.

A further object of our invention is the provision of a blind fastenerof the aforementioned character which is characterized by the fact thatthe aforesaid driver is composite in nature, that is, performs aplurality of functions. To accomplish the plurality of functions, thedriver includes a driving portion and a locking portion or ring, saiddriving and locking portions having a line of demarcation therebetweericonstituted by a shear zone which is frangible and which is adapted tobe sheared immediately prior to the shearing of the shear area of theassociated carrier.

An associated object of our invention is the provision of a blindfastener of the aforementioned character wherein the aforesaidsecurement member incorporates a head portion having a locking recesstherein, and said locking recess is adapted to receive the lockingportion or ring of said driver in locking relationship simultaneouslywith the completion of the deformation of the lower extremity of saidsecurement member into the desired securement ring configuration.

Therefore, when the desired formation of the securement ring isaccomplished, physical evidence of such accomplishment is presented bythe permanent reception and retention of the aforesaid locking portionof said driver in the locking receptacle and in the head of thesecurement member. Of course, the shearing action which results from thepositive engagement of the locking portion of the driver and thepositive deformation of the relevant extremity of the securement memberalso provides physical indication of the achievement of the desiredconfiguration on the inner extremity of the blind fastener.

A further object of our invention is the provision, in a blind fastenerof the aforementioned character, of a combination of surfaces anddimensions, to be alluded to in detail hereinbelow, which result in afastener which is completely capable of accommodating different gaugesof material, different configurations of material and which isreasonably grip insensitive, that is, capable of securing materials ofdifferent gauges in secure relationship and contiguity with each other.

An additional object of our invention is the provision of a method ofinstalling the aforesaid fastener which includes the steps of relativelymoving the driver and the carrier to accomplish corresponding relativeaxial movement of the extremity of the securement member over thecorresponding forming ring of the carrier to accomplish the axial andradial deformation of said extremity into a securement ring whichengages the inner surface of an object in an annular zone remote fromthe edge of the blind hole. A further step involves the successiveshearing of the shear area of the driver and shear zone of the carrierto leave a minimal residual structure at the external surface of theblind fastener which can subsequently be buffed or abraded away.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a vertical elevational viewillustrating the carrier incorporated in the blind fastener;

FIG. 2 is a bottom plan view taken from the broken line 2-2 of FIG. 1;

FIG. 3 is a side elevational view of the securement member associatedwith the carrier of the blind fastener;

FIG. 4 is a vertical sectional view taken on the broken line 4-4 of FIG.3;

FIG. 5 is a vertical sectional view similar to FIG. 4 but showing aslightly different configuration of securement member;

FIG. 6 is a side elevational view of an initial state of a driver blankprior to its being subjected to operations adapting it for utilizationin the fastener combination;

FIG. 7 is a vertical sectional view taken from broken lines 6-6 of FIG.6;

FIG. 8 is a sectional view showing a step in the preparation of thedriver blank of FIGS. 6 and 7 for fastener application;

FIG. 9 is a side elevational view of the assembled elements of the blindfastener prior to the subjection of the fastener to additional steps offabrication;

FIG. 10 is a schematic view illustrating the utilization of diedeformation on the shank of the carrier portion of the blind fastener;

FIG. I1 is a view similar to FIG. 10 showing the completion of the diedeformation of said shank;

FIG. 12 is a composite view illustrating the relationship betweenvarious elements of the blind fastener and the corresponding orifices injuxtapositioned sheets of material together with a side view ofa typicalinstalling device;

FIG. 13 is an enlarged vertical sectional view showing the manner inwhich an installation tool can be utilized in conjunction with oneembodiment of the blind fastener of the invention prior to energizationof the tool;

FIG. 14 shows the completion of the installation steps which result inthe permanent affixation of the fastener in the corresponding openings;

FIG. 15 is a vertical, enlarged partly sectional view showing analternative embodiment of the blind fastener of the invention prior toits final securement in the associated structure;

FIG. 16 is a view corresponding to FIG. 15 showing the termination ofthe securement steps;

FIG. 17 is a partially sectional view showing the application of analternative embodiment of fastener of the invention;

FIG. 18 is a view similar to FIG. 17 showing the completion of theinstallation of the fastener of FIG. 17;

FIG. I9 is a view showing the carrier in elevation; and

FIG. 20 is a vertical sectional view of the securement member.

DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION Referring to thedrawings, and particularly to FIGS. ll l3 thereof, we show a blindfastener 10, FIG. 9, which includes a carrier 12, FIG. I, a securementmember 14 and a driver 16.

The carrier 12, as the best shown in FIG. ll of the drawings, isprovided with a forming area or ring 18 at its lower extremity, saidarea or ring 18 being subtended by a relatively massive foot 20 tosustain the loads to which the forming area or ring 18 is subjectedduring the application of the fastener 10 in a desired structure. The.diameter of the foot 20 is such as to be receivable in correspondingopenings or holes in the parts to be secured in operative relationship.The transition between the lower and upper extremitiesof the formingring 18, which is, of course, a portion of the carrier 12, is a radiuswhich is approximately between one-eighth and one-fifteenth of thediameter of the holes in which the fastener I0 is located, such diameterbeing dependent also on the sharpness of formation of the deformedportion of the securement member to be achieved.

The distance h," FIG. 1, between the end of the threaded portion 22 ofthe carrier 12 and the upper extremity of the foot 20, that is, theheight of the forming ring 18, is determined by the total thickness ofthe parts to be fastened in operative relationship with each other. Thegrip range or tolerance on a sevensixteenths inch diameter fastener isabout plus or minus 0.03 inches. For example, in the range of 0.140 to0.170 total sheet thickness, the value of h" is about 0.080. If thetotal sheet thickness was 0.75 inches, the value of h would be about0.595 inches. Therefore, as can be readily determined, the height h ofthe ring 18 will vary direction with the thickness of the sheets orother structures to be fastened together. Obviously, the thicker thestructure to be fastened, the greater the height.

As previously mentioned, the forming ring 18 is provided with a radiusto accomplish the outward and turning moment of the relevant extremityof the securement member 12 in a manner to be described in greaterdetail below. We have found that a satisfactory radius to accomplish thedesired result is one-tenth of the hole diameter although there is arelatively wide range of approximately one-eighth to one-fifteenth ofthe hole diameter available, but superior formation of the deformableportion of the securement member 12 occurs in one-tenth hole diameterrange.

Incorporated in the stem or shank 26 of the carrier 12 is a shear orbreak-off area 28 constituted by a groove 32. The location of the sheararea or groove 32 is determined by the thickness of the sheets ofmaterial or structures to be fastened together by the fastener since, aswill be rendered apparent from the further consideration of the mannerof installation, the lower portion of the groove must be disposed at orabove the external surface of the sheets or structures being fastened. Athread 38 continuous with the thread 22 in its pitch and diameter isprovided on the upper extremity of the shank 26.

The thread portions 22 and 38 on the carrier 12 are preferably finethreads. For example, on a fivesixteenths diameter, shank 26 where theforming ring 18 has a seven-sixteenths diameter, the preferred thread isa 5/16-32 or even a 5/16-40. The fine thread provides, as will bedescribed in greater detail below, significant mechanical advantages incooperation with the driver 16 which materially assists in the formationof the proper configuration at the lower extremity of the securementmember 14 and also provides a greater difference between the thread rootdiameter and the diameter of the shear groove or area 28.

The carrier 10 may be fabricated from any desired material, but we havefound that such materials as Armco 17-4PI-I aged to 200,0O0/in Ti 6Al-4V, Inco 717, and Rene 41 are extremely adaptable for this particularapplication.

The surface condition on the forming ring 18 is not critical; suitabledeformation of the relevant extremity of the securement member 14 can beachieved where the finish has been produced by a carbide cutting toolwith no other additional treatment. Furthermore, if the.

surface is rolled on the ring 18, correspondingly excellent results tothose achieved by other means are obtained.

Disposed in encompassing relationship with the lower extremity of thecarrier 10 is the securement member 14, said securement member beingconstituted by a tubular bushing 40 which incorporates a longitudinalbore 42, said bore 42 being constituted by a substantially cylindricalportion 44 terminating at its upper extremity, as best shown in FIG. 4of the drawings, in

a locking receptacle 46 of frusto-conical configuration. The wall of thebore 42 terminates at its lower extremity in a radiused section orportion 48 which, as best shown in FIG. 13 of the drawings, is disposedin overlying relationship with the radius provided on the forming ring18 immediately above the foot 20 which subtends the ring 18.

Provided on the upper extremity of the bushing 40 is a frusto-conicalhead 52 which is adapted to be received in a corresponding receptacle orrecess 54 formed in the outermost 56 of two sheets of material 56 and58, as best shown in FIG. 13 of the drawings. Of course, the blindfastener 10 of the invention can be provided with a securement member 14defined by bushing having a head shape of any desired configuration, andthe depiction of a frusto-conical head portion in the drawings asexemplified in one embodiment of the invention, is not intended to limitthe concept thereof to a particular head configuration.

Disposed below the frusto-conical head 52 of the bushing 40 is acylindrical shoulder 57 provided with a land 59. The dimension a whichis shown in FIG. 3 as including the distance between the top of the head52 and the land 59 of the shoulder 57 is usually substantiallyequivalent to the total thickness of the superimposed sheets 56 and 58of material to be secured in operative relationship with each other, asbest shown in FIG. 13 of the drawings.

A forming foot 60 is provided upon the lower extremity of the bushing 40and its lower extreme end is provided by the radiused wall section 48 ofthe bore 42.

The foot 60 has an axial external surface 64 whose diameter is such asto be receivable in the contiguous openings formed in superimposedsheets 56 and 58, as best shown in FIG. 13 of the drawings. The lengthof the axial external surface 6 1 of the foot 60 is about oneeighth ofthe diameter of the holes through which the foot is inserted. Forinstance on a 7/l6 inch hole, the length would be approximately 0.055inch.

interposed between the shoulder 56 and the foot 60 is an elongatedcylindrical groove 68, which operates, in a manner to be described ingreater detail below, in conjunction with the foot 60 to facilitate theformation of a desired configuration of the lower extremity of thesecurement member 14. 7

Since the forming of the lower extremity of the bushing 40 by axialmovement against the forming ring 18 involves considerable cold workingof the material from which the bushing is fabricated, it is necessary toutilize a metal which has adequate elongation properties and a fairlyhigh degree of work hardening. In many applicationsancillarycharacteristics such as corrosion resistance and freedom fromstress corrosion are important. Furthermore, as the lower extremity ofthe bushing 40 is deformed, it is desirable that the material becharacterized by low galling as it slides over the forming ring 18 ofthe carrier 12.

Among the materials which have been utilized in prototype blindfasteners has been Armco steel alloy 15-16WR. A typical bar of thismaterial has the following solution annealed properties:

Ultimate 0.2% Reduction Hardness Tensile yield elong. of Area KSI KSIWhen the material is subjected to cold working equal to 26.5 percentcold reduction, the following properties have been determined:

Ultimate Reduction Tensile KSI 0.2% Yield KSI of Area The abovementioned material is also characterized by high resistance tocorrosion, stress corrosion, high temperature oxidation and gallingwhich are the characteristics desirable for a properly functioningbushing 40. Another satisfactory material is Allegheny Ludlum A-286solution annealed.

Titanium bushings have been fabricated from Ti 3a1-2-l /2V, whichprovides the most effective bushing from a strength standpoint. This isparticularly the case if this particular material can be obtained withapproximately 35 percent elongation. Other Titanium alloys have beenexperimented with, but they are either too hard, too weak or toodifficult to form.

The wall thickness of the bore 42 and the thickness of the foot 60, bothmeasured radially of the axis of the bore 42, determine the strength andthe configuration of the formed securement ring 70 of the bushing 40, asbest shown in FIG. 14 of the drawings, when the complete installation ofthe fastener 10 has been accomplished.

Therefore, it can be readily ascertained that the thickness of the wallof the bore 42 in the region of the groove 68 is determined in themanner in which the grooved portion and the foot portion of the bushingare deformed even though, after the forming of the securement ring 70,as best shown in FIG. 14 of the drawings, the groove has been eliminatedby the forming action of the foot 20 and the forming ring 18 of thecarrier 26.

No particular finishing operation is required for surfacing the bushing40 since conventional tools provide adequate surface finish.

An alternative bushing configuration 80 is shown in FIG. 5 of thedrawings, and is distinguishable from the bushing 40 in the provision ofa tapered wall 82 for the grooved area of the bushing. This bushingconfiguration is utilized where the necessity for extreme preload orfilling of the openings in the sheets to be secured in operativerelationship is indicated. Of course, variations in the configurationsof the wall of the grooves portion of the bushing constituting thesecurement member 141 may be dictated by specifics of application, butsuch variations will obviously fall within the broad scope of theteachings of the invention.

The driver 16 incorporated in the fastener is shown in completed form inFIGS. 9 and 12-13 of the drawings. However, since the driver 16 issubjected to a series of fabricating steps to achieve the finalconfiguration of FIGS. 9 and 12-13, reference is made to FIG. 6 of thedrawings which shows a blank 86 fabricated from stock. After therequisite length of hexagonal stock has been cut, it is drilled toprovide the bore 88 and turned to provide the groove 92. However, itshould be understood that references herein to specific modes ofmanufacture do not have a limiting connotation because other modes andoperations will be apparent to those skilled in the art which will beequally satisfactory to those disclosed, and the disclosure herein ofmanufacturing techniques is intended to support claims to the best knownmethod of fabricating the disclosed blind fastener.

In turning the groove 92, a wall thickness of approximately 0.005 inchis permitted to remain and on a 7/16 inch diameter fastener, the grooveis about 0.03 inch wide.

After the blank 86 has been fabricated, it is placed in an appropriatepress 94 to collapse the groove 92 axially. The blank 86, as best shownin FIG. 8 of the drawings, is then characterized by the fact that ashear or frangible zone 98 has been provided between an upper drivingportion 102 and a lower locking ring or portion 104 of the resultingdriver 16. A driving surface or engagement portion 107 is provided onthe lower extremity of said upper driving portion 102 to engage the head52 of the securement member 14 in a manner to be described in greaterdetail below. There is also an internal bulge 106 in the wall of thebore 88 attributable to the collapsing of the groove 92.

To eliminate this bulge, the bore 88 is drilled and is subsequentlytapped to providea fine thread corresponding to the thread portions 22and 38 provided upon the carrier 12. The relationship of the driver 16with the carrier 12 and securement member 14 when all of the elementsare assembled in operative relationship is best shown by the sectionalview of FIG. 13 wherein the locking portion or ring 104 of the driver 16is shown as partially received within the frusto-conical locking recess46 provided at the upper extremity of the bore 42 of the bushing 40constituting the securement member 14.

It will be noted that, when the blind fastener 10 is inserted in thecorresponding openings in the sheets 56 and 58, as best shown in FIG. 13of the drawings, the frusto-conical locking ring or portion 104 of thedriver 16 is partially located within the confines of the locking recess46 so that the shear zone 98 of the driver is disposed above the planeconstituted by the outer surface of the uppermost sheet 56 of the pairof sheets 56 and 58. It will also be noted that the shear area 28 of thecarrier 12 is disposed below the lower extremity of the driver 16.

Although the fabrication of the driving and locking portions of thedriver 16 has been disclosed as accomplished from a unitary blank, itwill be obvious to those skilled in the art that different modes ofcreating the same relationship can be accomplished as by resistancewelding a separately fabricated locking portion or ring to the drivingportion, or by bonding.

Of course, it is essential that the locking portion 104 of the driver bepositively attached to the driving portion 102 so that, in the initialstages of installation of the blind fastener, the driving and lockingportions act as a unitary structure and so that the locking portion orring will not act as a lock nut in relationship to the driving portion102. The material from which the driver 16 is fabricated can be of anytype compatible with the other components of the blind fastener 10 fromthe viewpoints of galvanic action, thermal expansion, strength,temperature requirements and reasonable freedom from gallingparticularly in the threads and between the heavy drive surface 107 atthe lower extremity of the driving portion 102, FIG. 8, which engagesthe top surface of the head 52 of the bushing 40.

Suitable materials include Armco l7-4Pl-I aged to H.900 which works wellon a carrier shank 26 of the same type of material in conjunction withan Armco -16WR bushing.

With a titanium fastener the driver 16 would preferably be fabricatedfrom Beta III or Ti 6A AL 4V or Prior to assembly of the variouscomponents of the blind fastener 10, the threaded portions 22 and 38 ofthe shank 26 are precoated with a light film of Molybdenum disulfidepowder either by dipping or spraying. The securement member 14 is thenplaced on the carrier 12 and the driver 16 threaded upon thecorresponding threads of the carrier 12. If desired, additionallubrication can be applied to the threads and the driver 16 then screweddown to firmly hold the securement member 14 against the forming ring18. Prelubrication of the assembly in this manner lubricates theinter-engaged threads, the tapered engagement of the locking ring orportion 104 and the locking receptacle 46, the internal bore 42 of thesecurement member 14 and he adjacent surfaces of the forming ring 18 andthe radius portion 48 of the bore 42.

With the component parts of the blind fastener 10 assembled in the abovedescribed manner, the shank 26 of the carrier 12 is placed between diesections 1 12 and 114 to impart a hexagonal configuration 118 to theprotruding portion of the shank 26, which prevents the components frombeing dissembled from one another and provides drive surfaces upon theprotruding portion of the shank 26 of the carrier 12, as best shown inFIGS. 12-14 of the drawings.

The driving or installation of the blind fastener 10 can be accomplishedby the utilization of a wide variety of installation tools, but, in therotary driving configuration which has been described hereinabove, atool is utilized which incorporates a frame 122 having a hexagonalreceptacle 124 for the reception of the hexagonal driving portion of thedriver 16. The hexagonal portion of the shank 26 of the carrier 12 isreceived in a correspondingly shaped receptacle 128 of the drivesprocket of an impact wrench or the like.

After the installation of the respective components of the blindfastener 10 in the associated installation tool, the blind fastener isinserted into the corresponding openings of the respective sheets 56 and58 to locate the fastener 10 in the orientation shown in FIG. 13 of thedrawings. Rotation of the socket 132 causes relative movement betweenthe shank 26 of the carrier 12 and the driver 16 causing the driver tomove downwardly toward the outer surface of the sheet 56 while causingthe lower extremity or foot of the carrier 12 to be drawn upwardlytoward the underside of the sheet 58.

Of course, the relative distance travelled by the carrier 12 is muchgreater than the distance that the driver moves downwardly to engage itsheavy driving or engagement face 107 with the upper surface of the head52 of the bushing 40 and to drive the locking ring or portion 104 intothe corresponding receptacle 46 of the bushing 40. The downward movementof the locking ring 104 begins during the radial and upward axialmovement of the foot or extremity 60 of the bushing 40 into thesecurement ring configuration shown at 70 in FIG. 14 of the drawings.

As the shank 26 is turned by the drive socket of the tool to back it outof the driver 16, all of the components of the fastener are pulledtoward each other while providing some spinning action on the bushing 40during the formation of the securement ring 70.

There may be a semantic question arising as to the use of theterminology for the driver 16 since the carrier 12 is actually rotatedby the action of the impact wrench utilized to install the fastener.However, the carrier 12 actually acts as a lead screw to urge the driver16 downwardly at the final moments of the assembly of the components tocause the locking ring 104 to deform into the space remaining betweenthe wall of the locking recess 46 of the bushing 40 and the perimeter ofthe remaining portion of the carrier 12 and to ultimately separate fromthe driver after being driven deeply into the locking recess untiltightly wedged between recess and carrier, as best shown in FIG. 14 ofthe drawings.

The torque output of the impact wrench utilized as an installation too]must be set at a value above the breakoff torque of the shear area 28 ofthe carrier 12. For example, on a 7/16 diameter blind fastener with a0.02 inch breakoff groove 32, the breakoff torque is about 60 foot lbs.Thus, it is desirable that the torque wrench be set for its maximumtorque of approximately 250 foot lbs. to achieve the greatest speed ofinstallation and the desired rupturing of the shear area 28 of thecarrier 12.

It is not necessary to remove burrs on the blind side of the holes sincesuch burrs do not detract from the formation of the locking ring 70. Asa matter of fact, when the locking ring is formed, a burr pocket 152 isprovided, as best shown in FIG. 14 of the drawings, which accommodatesthe burrs. This pocket can also receive an elastomeric ring which isinstalled on the bushing 40 adjacent the land 58 during the assembly ofthe components of the bushing. The burr pocket allows the sheets to begripped externally of the burr, whereas conventional fasteners bulge outagainst the burr or the sharp corner where the burr was creating astress concentration area of annular configuration.

Because of the manner in which the sheets are gripped externally of theburr over a significant area annular to the hole, as best shown in FIG.14 of the drawings, an extremely strong attachment of the sheets 56 and58 to each other is achieved. For instance on a 7/l6 diameter hole, thegrip area is over l/32 inch wide.

Another important aspect of the blind fastener 10 is that it requires anextremely small blind side clearance, that is, the space between theunderside of the sheet 58 and an adjacent structure. For instance, on a7/ 16 inch hole size, the blind fastener 10 can be properly installedwith less than 3/16 inch clearance. Other fasteners of the same sizerequire at least l/2 inch clearance and frequently over 1 inchclearance. I

Due to the interaction of the locking ring or portion 104 of the driver16, and the securement ring 70, the holes are completely filled and abearing pre-stress is exerted upon the walls of the holes. The provisionof the locking ring or portion 104 also serves, as best shown in FIG. 14of the drawings, to provide an axial preload on the residual shank, thusinsuring high fatigue capability. As the installation tool increases theload upon the shank 26 of the carrier 12, the shank lengthens, thus withan 8,000 lb. pull on a 5/ 16 stem or shank (root diameter of 0.277)having an area of 0.06 sq. inch, the stress is 8,000/0.06 or 133,000lb.sq. inch. The elastic elongation of the stem is then 133,000/El32,000/(29Xl0) 0.0046 in/in. In a A inch (residual stem) this is 0.001]inch.

After the driving portion breaks off, the residual shank remainingwithin the holes tends to seat the locking ring 104 more deeply in thelocking recess 46 to provide for a maximum grip effect on the securedsheets of material.

During the installation of the fastener, the foot 60 of the bushing isturned 90 to engage the inner surface of the sheet 58 over a substantialannular area. In other words, the axially oriented wall 64 of the foot60 of the bushing impinges on the underside or inner surface of thesheet 58, as best shown in FIG. 14, and the foot is connected to theremainder of the bushing by an arcuate portion 166 so that variations inthe sheet composite thickness do not prevent them from being gripped bya flat surface. In other words, deviations in the thickness are takencare of by disturbing the arch and not the gripping foot.

The utilization of an elastomeric ring in conjunction with the residualburr pocket 152 has been referred to hereinabove. However, thisadditional elastomeric ring is not really essential because the blindfastener is essentially leak proof. The bushing 40 is swelled so tightlyinto the holes in the adjacent sheets that irregularities of the holesare filled and the swelling is accomplished from both ends of thebushing by the cooperative action of the forming ring 18 and the lockring 104 moving toward each other. In conventional blind fasteners, oneforming member is translated through a securement member and the metalflow is in one direction which tends to move the metal of the securementmember up and out of the hole on the external side.

In other words, in the blind fastener of the present invention, there isa squeezing action which takes place because of the interaction of thedriver 16 and the forming ring 13 moving dynamically toward each otherto cause the complete formation of the securement ring 70 and thecomplete installation and deformation of the locking ring 104.

In other words, the forming ring 18 by fabricating the securement ring70 seals the internal diameter of the bushing 14 at one end and thelocking ring 104 seals it at the other end. After the shearing of thefrangible zones of the driver and carrier, the locking ring threads aretightly engaged and the tapered wall of the locking receptacle 46actually collapses or reduces the diameter of the locking ring 104 toincrease the seal between the ring and the threads.

Furthermore, as the foot 60 of the bushing 40 turns, it work hardens andprovides a massive ring of increased strength to resist the outward flowof metal as it swings around the curling ring 18. The resistance tooutward flow causes the foot 60 to move upwardly along the path of leastresistance and pull the sheets together. In other words, the initialradial movement of the foot 60 over the forming ring 18 is convertedinto the axial movement which brings the previously axially orientedwall 64 of the foot into a horizontally planar engagement of theunderside of the sheet 58.

Just prior to the breakoff of the shank 26 of the carrier 12, theincreased elongation of the breakoff portion of the shank referred tohereinabove separates the lock ring 104 from the driving portion 102thereof and since the lock ring 104 cannot turn, it actually screwsitself on the threaded section 22 further into the locking receptacle 46of the bushing 40.

Because of the dynamic action of the locking ring 104, the stem lockingstrength of the fastener of the invention is maximal. In actualexperiments we have discovered that it takes over 6,000 lbs. force topush the stem out of the 7/16 fastener using 17-4 material for thelocking ring and the stem. The locking ring 104 has three full threadsin its bore and a 20 external taper which, while it fits into thelocking receptacle 46, it is held upwardly from the upper surface of theheat at 52 of the bushing 40 by approximately 0.03 inches prior todriver.

Consequently, when the locking ring 104 is forced into the taperedreceptacle 46 of the bushing 40, the bushing is expanded, the lockingring is compressed onto the threads or carrier and the maximum tightnessof the locking ring is achieved.

Moreover, the blind fastener 10 is characterized by the cooperatingshear zones or areas of the carrier 12 and driver 16 whereby the lockingring 104 breaks or shears off the driver 16 prior to the severance ofthe shear zone on the carrier 12, which insures that the locking ring isalways located in the locking receptacle 46 of bushing 40 to the maximumdepth and seated extremely tightly in the receptacle because of theinterference fit between the receptacle and the locking ring and thefact that the driver forces the bushing downwardly around the lockingring to deform bushing metal around the ring between the holes in thesheets and the locking ring and shank of the carrier 12.

The resultant compressive forces exerted upon the sheets 56 and 58 arelocated in the most effective zones since the face 64 of the bushing 40is displaced outwardly of the edge of the hole in the lowermost sheet58, best shown in FIG. 14 of the drawings. In conventional bulbingfasteners, the compressive loads are exerted at the corners of the holesin both a radial and an axial direction, whereas in the blind fastener10 of the invention, the loads are completely axial as caused by thecooperative effects and squeezing force of the locking ring 104 andsecurement ring 70.

Of utmost importance is the fact that the foot 60 of the bushing 40 isof relatively large diameter and is secured to the head 52 of thebushing 40 by the reduced wall section provided by the groove 68. Thereduced wall section applies a turning moment to the foot 60 during theinstallation of the fastener 10, which creates the controlled movementof the foot 60 to cause the foot face 64 to turn upwardly and moveaxially against the underside of the sheet 68. The height of the grooveprovides a controlled distance which allows the movement of the surface64 of the foot into engagement with the underside of the sheet 58 andthe resultant pullup of the sheets 56 and 58 prior to the exertion ofthe massive compressive forces and swelling of and displacement of themetal due to the final driving of the locking ring 104 into thecorresponding locking receptacle 46 by the driver 16. Therefore, thesheets 56 and 58 cannot be misassembled because metal has been squeezedbetween them prior to the exertion of the massive compressive forcesalluded to hereinabove.

Of course, the inherent mechanics of the blind fastener 10 entail axialmovement of the foot 20 of the carrier and the driver 16 toward eachother. The previously discussed embodiment of the invention accomplishessuch axial movement by rotating the shank 26 of the carrier 12.

However, such axial loads can be created by axial pulling upon relevantportions of the alternative embodiments of the fastener rather thanrelative rotation of the components thereof as in the previouslydiscussed embodiments. In the blind fastener 180 shown in FIGS. 15 and16 of the drawings, the carrier 182 has a forming ring 184 and a sheargroove 186. The upper extremity 188 of the bushing 187 is headed so asto provide six castellations having steeply sloping slot bottomsextending radially from the bushing internal diameter at a level wellbelow the surface of the head of the bushing, to the surface of the headof the bushing in a zone more or less determined by the OD of theupstanding castellations.

The cross-sectional area of the castellations 192 is sufficient to carrya force, as applied axially to form the bottom end of the bushing intothe locking ring 194 while an axial load is imposed the carrier 182.

After the lower extremity or foot of 184 of the bushing 187 is formedinto the gripping position, the application of an increasing downwardforce on the castellations begins to compress the castellations to causethem to move downwardly'and inwardly and fill the aforementioned slotsuntil the residual metal has moved into locking relationship with thereceptacle in the upper end of the bushing and the locking groove 196provided in the carrier 184.

In the embodiment 210 of the fastener shown in FIGS. 17-20 of thedrawings, the carrier 212 is provided with an upwardly exposed cuttingedge 214 on a slightly larger diameter portion of the shank of thecarrier and an annular recess 216 is provided to receive cut material.Pull rings 218 are provided on the shank of the carrier 212 tofacilitate the exertion of a pulling force on the shank of the carrier212.

The bushing 222, FIG. 20, is provided with a downwardly exposed step 224and an outward annular recess 226 above said step.

As an axial pull is imposed upon the shank of the carrier 212 throughpull rings 218, the deformation of the lower extremity of the bushing222 is initiated while the cutting edge 214 begins shearing the bushingstep 224.

The sheared material from the step 224 is deposited initially in theannular recess 216 in the stem until further movement of the carrier 212causes juxtaposition of the recess 216 with the corresponding recess 226in the bushing and the recess 226 receives the additional deposit ofmaterial.

Consequently, the step material will be deposited in the cooperativerecesses prior to the shearing of the shank of the carrier 212 from theportion of the shank deposited in the bushing 222.

We claim:

1. In a blind fastener for insertion into an opening from one side of anobject, the combination of: an elongated carrier having a formingportion at one extremity, said one extremity having a diameterpermitting its insertion through said opening and said forming portionincorporating an annular radiused lateral forming surface being openthroughout the radial outer periphery thereof and being directed towardthe other extremity of the carrier; a tubular securing member having anenlarged head at one extremity with a locking receptacle therein and anopposed deformable portion with an intermediate recess at the otherextremity, said securing member encompassing said carrier with saiddeformable portion adjacent said forming portion, the outer diameter ofsaid one extremity being substantially equal to said deformable portionof said securing member; and a driver encompassing said carrierintermediate its extremities axially, outwardly of said securing member,said driver having a tool engageable portion and a locking portionjoined together by a frangible zone, said driver having an engagementportion intermediate said tool engageable portion and said lockingportion for engaging said enlarged head to axially urge said securingmember against said forming surface to deform said deformable portion ofsaid securing member into secure engagement with the other side of saidobject and to lock saidlocking portion of said driver in said lockingreceptacle and said enlarged head of said securing member in saidopening.

2. A blind fastener as defined in claim 1 in which said lockingreceptacle and said locking portion are frustoconical.

3. A blind fastener as defined in claim 1 in which said securing memberhead has an upper surface adjacent said locking receptacle and saidengagement portion of said driver is engageable with said upper surfacewhen said locking portion is driven into said locking receptacle.

4. A blind fastener as defined in claim 3 in'which said upper surface ofsaid enlarged head and said engagement portion have conformingconfigurations to facilitate the engagement of said head and saidengagement portion.

1. In a blind fastener for insertion into an opening from one side of anobject, the combination of: an elongated carrier having a formingportion at one extremity, said one extremity having a diameterpermitting its insertion through said opening and said forming portionincorporating an annular radiused lateral forming surface being openthroughout the radial outer periphery thereof and being directed towardthe other extremity of the carrier; a tubular securing member having anenlarged head at one extremity with a locking receptacle therein and anopposed deformable portion with an intermediate recess at the otherextremity, said securing member encompassing said carrier with saiddeformable portion adjacent said forming portion, the outer diameter ofsaid one extremity being substantially equal to said deformable portionof said securing member; and a driver encompassing said carrierintermediate its extremities axially, outwardly of said securing member,said driver having a tool engageable portion and a locking portionjoined together by a frangible zone, said driver having an engagementportion intermediate said tool engageable portion and said lockingportion for engaging said enlarged head to axially urge said securingmember against said forming surface to deform said deformable portion ofsaid securing member into secure engagement with the other side of saidobject and to lock said locking portion of said driver in said lockingreceptacle and said enlarged head of said securing member in saidopening.
 2. A blind fastener as defined in claim 1 in which said lockingreceptacle and said locking portion are frusto-conical.
 3. A blindfastener as defined in claim 1 in which said securing member head has anupper surface adjacent said locking receptacle and said engagementportion of said driver is engageable with said upper surface when saidlocking portion is driven into said locking receptacle.
 4. A blindfastener as defined in claim 3 in which said upper surface of saidenlarged head and said engagement portion have conforming configurationsto facilitate the engagement of said head and said engagement portion.